This invention relates generally to the field of jacks, and, more particularly, to jacks actuated by screw assemblies.
Screw jacks are known to be used in various applications, including leveling and supporting vehicles such as recreational vehicles and trailers. Such jacks have a single screw that is rotated by way of a motor and gear assembly to raise and lower the vehicle.
U.S. Pat. No. 4,067,543 to Orth et al. discloses a retractable jack having a jackscrew threaded in a jackscrew nut. A motor and associated gear assembly rotatably drives the jackscrew. Orth is limiting in that only a single jackscrew is provided and, therefore, no redundancy is provided in the event of failure of the screw. Additionally, significant torque is required to lift the load with the use of a single screw.
It is an object of the present invention to provide a jack that reduces or wholly overcomes some or all of the difficulties inherent in prior known devices. Particular objects and advantages of the invention will be apparent to those skilled in the art, that is, those who are knowledgeable or experienced in this field of technology, in view of the following disclosure of the invention and detailed description of preferred embodiments.
The principles of the invention may be used to advantage to provide a jack having a plurality of screws. The plurality of screws allows for smaller diameter screws to be used, easing manufacturing and improving availability. Additionally, smaller diameter screws are less affected by rotational friction, thereby reducing the torque required to operate the jack. Using a plurality of screws also provides redundancy of components, and, therefore, enhances safety.
In accordance with a first aspect, a jack includes a motor, a gear assembly operably connected to the motor, a ram, and a plurality of screw assemblies driven by the gear assembly to move the ram.
In accordance with another aspect, a jack includes a motor. A gear assembly has a pinion gear operably connected to and driven by the motor, and a plurality of screw gears. Each screw gear is driven by the pinion gear. A ram is slidably received in a housing, and a thrust plate is secured to the housing. Each screw of a plurality of screw assemblies is operably connected to the ram, axially fixed with respect to the thrust plate, and driven by a screw gear to move the ram with respect to the thrust plate.
In accordance with another aspect, a jack includes a motor and a gear assembly. The gear assembly has a pinion gear operably connected to and driven by the motor, and three screw gears. Each screw gear is driven by the pinion gear. A ram is slidably received in a housing, and a thrust plate is secured to the housing. Each of three ball screws is operably connected to the ram, axially fixed with respect to the thrust plate, and driven by a screw gear to move the ram with respect to the thrust plate.
From the foregoing disclosure, it will be readily apparent to those skilled in the art, that is, those who are knowledgeable or experienced in this area of technology, that the present invention provides a significant advance. Preferred embodiments of the jack of the present invention can provide a jack that operates with reduced torque, has increased safety, and minimizes manufacturing costs. These and additional features and advantages of the invention disclosed here will be further understood from the following detailed disclosure of preferred embodiments.